The United States Navy began replacing and upgrading its ultra-high frequency (UHF) communications network in 1993 with the first launch of a new generation of military satellites

This new constellation of customized satellites was built by Hughes Space and Communications Company, which is now Boeing Satellite Systems, Inc.

Known as the UHF Follow-On (UFO) series, these 601 model satellites support the Navy's global communications network, serving ships at sea and a variety of other U.S. military fixed and mobile terminals. They are compatible with ground- and sea-based terminals already in service. The UHF Follow-On satellites are intended to replace the Fleet Satellite Communications (FLTSATCOM) and the Hughes-built Leasat spacecraft.

In March 1996, under a contract modification for $150 million, the Navy ordered a high-power, high-speed Global Broadcast Service (GBS) payload to be incorporated onto payloads F8 through F10. This GBS package is revolutionizing communications for the full range of the Defense Department's high-capacity requirements, from intelligence dissemination to quality-of-life programming. The first GBS payload was put into service in 1998, and the final one was launched in November 1999.

In November 1999, the Space and Naval Warfare Systems Command's Communications Satellite Program Office added an 11th satellite to the contract. This satellite was launched on December 18, 2003 and will help sustain the constellation into the latter part of the decade.Model 601 Platform
The UFO spacecraft has proven to be a very flexible platform for the evolution of critical advanced DOD communications services. These satellites consist of four different versions of the body-stabilized, three-axis Boeing 601 model platform.

The Boeing 601 satellite consist of two main modules. The bus module houses the bus electronics, propulsion subsystem, and battery packs. The payload module contains the communications equipment and antennas. The satellite dimensions when stowed were 11 feet high and 10.5 by 11.1 feet wide. Table one is a summary of various parameters for each of the four UFO satellite blocks.

The first seven satellites and F11 measure more than 60 feet long from the tip of one three-panel solar array wing to the tip of the other. Spacecraft F8 through F10 each have four solar panels on a side, making the spacecraft 75 feet tip to tip. These arrays generate a combined 2,500 watts of electrical power on the first three satellites, 2,800 watts for F4 through F7 and F11, and 3,800 watts for F8 through F10 with the GBS communications payload.

The arrays are folded against the spacecraft bus for launch, forming a cube roughly 11 feet per side. The satellites weigh an average of 2,600 pounds with the UHF payload, 3,000 pounds with the additional EHF payload, and 3,400 pounds with the GBS payload.

The Atlas rocket series was chosen to provide the launches from Cape Canaveral, Florida. The Atlas I rocket was used for the F1 through F3 satellites. The Atlas II was chosen for F4 through F8, and an Atlas IIA for F9 and F10. The Atlas IIIB was used to launch UFO F11.Increased Comm Capability with the UFO Birds
These UFO satellites were manufactured in El Segundo, California. Using a building-block approach, Boeing and the Navy enhanced the constellation's capabilities in stages. Satellites F1 through F3 carry UHF and SHF (super-high frequency) payloads to provide mobile communications and fleet broadcast services. Starting with F4, an additional EHF (extremely high frequency) payload was added to provide protected communications. F7 introduced an enhancement to the EHF package that essentially doubled traffic capacity in that band. The SHF payload was replaced by the high data rate GBS package on F8 through F10. F11 carries an enhanced EHF package and an upgraded UHF payload as well.

The UFO satellites offer DoD and the Navy increased communications channel capacity over the same frequency spectrum used by previous systems such as the FLTSATCOM and Leasat constellations. Each spacecraft has 11 solid-state UHF amplifiers and 39 UHF channels with a total 555 kHz bandwidth. The UHF payload comprises 21 narrowband channels at 5 kHz each and 17 relay channels at 25 kHz. By comparison, each FLTSATCOM platform offers 22 channels for two-way tactical communications. The 23rd channel on a FLTSATCOM carries the fleet broadcast service downlink. The F1 through F7 spacecraft include an SHF subsystem, which provides command and ranging capabilities when the satellite is on station as well as the secure uplink for Fleet Broadcast service, which is downlinked at UHF like its FLTSATCOM and Leasat cousins.

This new EHF Fleet Broadcast capability supersedes the need for the SHF fleet uplink and is replacing that communication function. With the launch of UFO F7 in 1996, the EHF package was enhanced to provide 20 channels through the use of advanced digital integrated circuit technology.

Some specifics communication information for some of the UFO satellites:

The GBS payload replaced the SHF payload on spacecraft F8, 9, and 10. This new package includes four 130-watt, 24 megabits-per-second (Mbps) military Ka-band (30/20 GHz) transponders with three steerable downlink spot beam antennas (2 at 500 nmi and 1 at 2,000 nmi) as well as one steerable and one fixed uplink antenna. This modification resulted in a 96 Mbps capability per satellite. The three UFO GBS equipped spacecraft gives DOD a near-global coverage (except for the polar regions).

The latest payload UFO F11 is most similar to F7, providing UHF and enhanced EHF communications. The UHF payload incorporates a new UHF digital receiver, providing two additional UHF channels and greater flexibility in configuring communication services. We are currently working to identify the two new frequencies associated with this new comm package on UFO F11.

Table 2 is the launch summary for the UFO constellation. Table three is a complete listing of all the known bandplans/frequencies (less the new UHF channel capability on UFO F11) being used by these satellites.